///代码基本来自LearnOpenGL网站
#ifndef MODEL_H
#define MODEL_H
#include "bhxjmesh.h"
#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>
#include<iostream>
#include<string>
#include<stb/stb_image.h>
#include "bhxjglinclude.h"
#include "bhxjglshader.h"
#include "bhxjmesh.h"
#include "BHXJControls_global.h"
using namespace  std;
class BHXJCONTROLS_EXPORT BHXJModel
{
public:

    BHXJModel()
    {

    }

    void Init(BHXJGLFUN *glcore,string path)
    {
        loadModel(path,glcore);
    }
    void Draw(BHXJGLShader shader)
    {
        for(unsigned int i = 0; i < meshes.size(); i++)
            meshes[i].Draw(shader);
    }
private:

    BHXJGLFUN *gl;

    /*  模型数据  */
    vector<BHXJMesh> meshes;
    string directory;
    vector<Texture> textures_loaded;
    /*  函数   */
    void loadModel(string path,BHXJGLFUN *glcore)
    {
        this->gl=glcore;
        Assimp::Importer import;
        const aiScene *scene = import.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);

        if(!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode)
        {
            cout << "ERROR::ASSIMP::" << import.GetErrorString() << endl;
            return;
        }
        directory = path.substr(0, path.find_last_of('/'));

        processNode(scene->mRootNode, scene);
    }
    void processNode(aiNode *node, const aiScene *scene)
    {
        // 处理节点所有的网格（如果有的话）
        for(unsigned int i = 0; i < node->mNumMeshes; i++)
        {
            aiMesh *mesh = scene->mMeshes[node->mMeshes[i]];
            meshes.push_back(processMesh(mesh, scene));
        }
        // 接下来对它的子节点重复这一过程
        for(unsigned int i = 0; i < node->mNumChildren; i++)
        {
            processNode(node->mChildren[i], scene);
        }
    }
    BHXJMesh processMesh(aiMesh *mesh, const aiScene *scene)
    {
        vector<Vertex> vertices;
        vector<unsigned int> indices;
        vector<Texture> textures;

        for(unsigned int i = 0; i < mesh->mNumVertices; i++)
        {
            Vertex vertex;
            // 处理顶点位置、法线和纹理坐标
            glm::vec3 vector;
            vector.x = mesh->mVertices[i].x;
            vector.y = mesh->mVertices[i].y;
            vector.z = mesh->mVertices[i].z;
            vertex.Position = vector;

            vector.x = mesh->mNormals[i].x;
            vector.y = mesh->mNormals[i].y;
            vector.z = mesh->mNormals[i].z;
            vertex.Normal = vector;

            if(mesh->mTextureCoords[0]) // 网格是否有纹理坐标？
            {
                glm::vec2 vec;
                vec.x = mesh->mTextureCoords[0][i].x;
                vec.y = mesh->mTextureCoords[0][i].y;
                vertex.TexCoords = vec;
            }
            else
                vertex.TexCoords = glm::vec2(0.0f, 0.0f);
            vertices.push_back(vertex);
        }
        // 处理索引
        for(unsigned int i = 0; i < mesh->mNumFaces; i++)
        {
            aiFace face = mesh->mFaces[i];
            for(unsigned int j = 0; j < face.mNumIndices; j++)
                indices.push_back(face.mIndices[j]);
        }
        // 处理材质
        if(mesh->mMaterialIndex > 0)
        {
            aiMaterial *material = scene->mMaterials[mesh->mMaterialIndex];
            // 1. diffuse maps
            vector<Texture> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
            textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
            // 2. specular maps
            vector<Texture> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
            textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
            // 3. normal maps
            std::vector<Texture> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal");
            textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
            // 4. height maps
            std::vector<Texture> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height");
            textures.insert(textures.end(), heightMaps.begin(), heightMaps.end());

            // return a mesh object created from the extracted mesh data
            return BHXJMesh(this->gl, vertices, indices, textures);
        }

        return BHXJMesh(this->gl,vertices, indices, textures);
    }
    vector<Texture> loadMaterialTextures(aiMaterial *mat, aiTextureType type,string typeName)
    {
        vector<Texture> textures;
        for(unsigned int i = 0; i < mat->GetTextureCount(type); i++)
        {
            aiString str;
            mat->GetTexture(type, i, &str);
            // check if texture was loaded before and if so, continue to next iteration: skip loading a new texture
            bool skip = false;
            for(unsigned int j = 0; j < textures_loaded.size(); j++)
            {

                if(std::strcmp(textures_loaded[j].path.C_Str(), str.C_Str()) == 0)
                {
                    textures.push_back(textures_loaded[j]);
                    skip = true; // a texture with the same filepath has already been loaded, continue to next one. (optimization)
                    break;
                }
            }
            if(!skip)
            {   // if texture hasn't been loaded already, load it
                Texture texture;
                texture.id = TextureFromFile(str.C_Str(), this->directory,false);
                texture.type = typeName;
                texture.path = str.C_Str();
                textures.push_back(texture);
                textures_loaded.push_back(texture);  // store it as texture loaded for entire model, to ensure we won't unnecesery load duplicate textures.
            }
        }
        return textures;
    }

    unsigned int TextureFromFile(const char *path, const string &directory, bool gamma)
    {
        string filename = string(path);
        filename = directory + '/' + filename;

        unsigned int textureID;
        gl->glGenTextures(1, &textureID);

        int width, height, nrComponents;
        unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
        if (data)
        {
            GLenum format;
            if (nrComponents == 1)
                format = GL_RED;
            else if (nrComponents == 3)
                format = GL_RGB;
            else if (nrComponents == 4)
                format = GL_RGBA;
            else {
                return 0;
            }

            gl->glBindTexture(GL_TEXTURE_2D, textureID);
            gl->glTexImage2D(GL_TEXTURE_2D, 0, static_cast<GLint>(format), width, height, 0, format, GL_UNSIGNED_BYTE, data);
            gl->glGenerateMipmap(GL_TEXTURE_2D);

            gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
            gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
            gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
            gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

            stbi_image_free(data);
        }
        else
        {
            std::cout << "Texture failed to load at path: " << path << std::endl;
            stbi_image_free(data);
        }

        return textureID;
    }
};
#endif // MODEL_H
